In two recent and marvelous Schubert Club International Artist Series recitals with harpsichordist Richard Egarr, cellist Steven Isserlis played Bach’s 5th Cello Suite, BWV 1011. That work includes a singular sarabande, shown here in in Anna Magdalena Bach’s hand:
The more I listen to this simplest and saddest of the cello sarabandes, the more I—taking a cue from Mr. Isserlis—am convinced of a larger idea behind it. In a blog entry, “A Few Little Thoughts on Playing Bach,” Stephen Isserlis offers a personal interpretation of the last two cello suites:
I believe that they represent the life of Christ, with the Fifth Suite portraying the Crucifixion, the Sixth the Resurrection. I have absolutely no evidence for this—it is really a feeling, not a theory, in fact; but I do find it an inspiring vision.
Perhaps there is some circumstantial evidence. First of all, there’s the cello tuning in the Fifth Suite: discordata, i.e. scordatura. The top string is dis-tuned down a step to G, maiming the instrument, in effect. It also happens that the C-minor Sarabande shares the triple meter and minor key of the final chorus of the St. Matthew Passion: (Remember that in the Baroque, key signatures of flat keys often lack the last flat.) What’s more, the bass in the second bar describes a downward motion similar to that of the Sarabande.
And is that a cross-figure hidden in the opening motive of the cello piece? 
This sort of thing was a common topos in the Baroque, clearly expressed, with text to match, in the motet, Komm, Jesu, Komm, BWV 229, where a Kreuzfigur graphically illustrates the growing burden of “the sour way.”
I get a little shiver when I see the image in three dimensions, as if the cross is moving to the right, supported by the half notes that bear it.
To explore the harmonic dimensions of the cello sarabande, I added upper parts to flesh out the harmony and “complete” the piece, much as one would realize a figured bass. Of course, the single line is complete by itself, but to my ear it implies a larger presence. One tantalizing possibility: this solitary bass remains on a palimpsest, “a parchment on which the original text has been effaced or partially erased, and then overwritten by another (OED),” as in the Archimedes Palimpsest, On Floating Bodies.
In this context, the solo cello line implies isolation, the voice crying: “My God, my God, why have you forsaken me?” The larger, unsounded harmonies provide conceptual completion, even comfort. Could this be what we are meant to “hear” in the Sarabande: a larger presence that envelopes the bass, a nimbus around it?
We’ll probably never know Bach’s intent. This crucifixion-by-sarabande, as Isserlis writes, “is really a feeling, not a theory, in fact; but I do find it an inspiring vision.” Through the depth of Bach’s faith and his penchant for embedding symbols in his music, the vision quavers before us.
Listen to a realization of the sarabande bass: